Recently, the memory device called PRAM (phase change random access memory) has been drawing attention. In PRAM, the microstructure of the recording layer is switched between the crystal phase and the amorphous phase, and the difference in electrical resistance value (hereinafter simply referred to as “resistance”) between these phases is used to store data. However, regarding PRAM, the following problems have been pointed out. In PRAM, the recording layer is turned into the crystal phase by passing a current therein to heat it to a temperature less than the melting point. On the other hand, the recording layer is turned into the amorphous phase by passing a current therein to heat it to a temperature more than or equal to the melting point and then being quenched. Thus, a relatively large current is needed to write data. Furthermore, crosstalk due to heat transfer is likely to occur. Thus, it is difficult to increase the packing density of PRAM. Furthermore, the phase change between the crystal phase and the amorphous phase requires a certain period of time and results in slow operating speed. Moreover, it is difficult to form each phase uniformly. Thus, the current path varies for each time of phase change and results in the variation of resistance.
To solve these problems, a memory device with the recording layer made of a superlattice stacked body (interfacial phase change memory, iPCM) has been proposed. In iPCM, by injecting a current into the recording layer, constituent atoms in the superlattice stacked body are reversibly interchanged with the microstructure of the recording layer left in the crystal phase. Thus, the resistance of the recording layer is changed to store data. In such iPCM, the position of the constituent atom is microscopically changed with the crystallinity of the recording layer maintained. Thus, compared with the aforementioned PRAM, the amount of current needed to write data is smaller, and crosstalk due to heat transfer is less likely to occur. Furthermore, the time required for state change is shorter, and the current path is more likely to be stabilized. Because of these advantages, iPCM is suited for the increase of packing density and speed enhancement. However, even in iPCM, there is demand for further improvement in recording density.